Magnets possess an inherent power to captivate and mystify us. I mean, right from the moment we first encounter their enticing culture, we usually do find ourselves inexorably drawn to their enigmatic forces. So, we might ask ourselves, how is it that a seemingly ordinary piece of metal is able to possess such an extraordinary ability to attract and repel? Well, let's start by admitting to the fact that the world of magnetism is shrouded in complexity that many of us would take some time to understand. And we also have to agree that these magnets are quite indispensable to our daily lives, which is why it is crucial for us to understand them better. Now, in this article, we will explore the magnets on a deeper level, giving you the fundamental principles governing how magnets work, and then close the article by shedding light on their remarkable real-life applications in various fields.
Historical Background
We begin by giving you a brief historical glimpse, tracing the origins of humankind's fascination with magnets. The history of magnets dates back a few centuries, and we can tell you that it is rich and fascinating. So, here is an overview of their historical significance;
Ancient discoveries - the discovery and use of magnets can be traced back to ancient civilizations, with the earliest known magnetic material being the lodestone, which is a naturally occurring magnetized mineral composed mainly of magnetite. Ancient cultures, such as the Greeks, Chinese, and Egyptians, were aware of the magnetic properties of lodestone as early as 600 BCE. They used it for various purposes, including navigation, divination, and religious rituals.
Chinese compass – secondly, one of the most significant advancements in magnetism occurred in China during the Han Dynasty (206 BCE - 220 CE). It was during this period that the Chinese invented the compass, which utilized the magnetic properties of lodestone. This compass revolutionized navigation, allowing sailors to determine their direction accurately and explore distant lands.
Arab scholars – fast-forward to the Middle Ages when Arab scholars made significant contributions to the understanding of magnets. You see, around the 8th century, Persian scholar Al-Kindi wrote about the attractive properties of lodestones and explored their use in navigation. Arab scientist Al-Biruni also studied magnets and wrote about their magnetic fields.
Scientific studies – come the 16th and 17th centuries, significant progress was made with regard to the scientific principles behind magnetism. During this time, William Gilbert, who was an English philosopher and physician, conducted extensive experiments with magnets and published all his findings in his book called 'De Magnete' in 1600. Gilbert essentially laid the groundwork for the scientific study of magnetism.
In the 18th century, scientists then began to understand the concepts of magnetic poles as well as the behaviour of magnets. French physicist Charles-Augustin de Coulomb formulated Coulomb's Law, which explained the force between magnetic poles and the inverse square relationship. This understanding of magnetic polarity and the behaviour of magnets basically paved the way for further advancements in the field. Then in the 19th century, a connection was made between magnetism and electricity, which now led to the development of electromagnetism. At this point, it was established that an electric current creates a magnetic field by a Danish physicist, Han Christian, and then later, the British scientist Michael Faraday expanded by formulating the laws of electromagnetic induction.
Magnetic Fields and Attraction/Repulsion
When we talk of magnetic fields, we are referring to invisible regions of influence that surround magnets and other magnetic objects. These fields are responsible for the attractive and repulsive forces observed between magnets. Essentially, the magnetic fields are created by magnets, electric currents, as well as moving charged particles, and they extend outward from a magnet in three-dimensional space, forming a continuous loop, which returns to the magnet. The strength and direction of the magnetic field are represented by magnetic field lines, whose density indicates strength, while closer lines indicate a stronger field. With regards to the attraction and repulsion between the magnets, we can start by stating that when two magnets approach each other, the magnetic fields do interact – they can either attract or repel. Opposite poles attract each other while like poles repel. The reason opposite poles attract is that the magnetic field lines from one magnet align and merge with the field lines of the other magnet, creating a more stable configuration. As for the repulsion, the magnetic lines try to move apart, which results in a force that pushes the magnets away from each other.
How are Magnetic Fields Created?
First of all, you need to understand that magnetism arises from the movement and alignment of electrons, specifically their intrinsic property known as spin. With that said, here is how the alignment of electrons within atoms leads to the creation of magnetic fields;
Electron spin – so, electrons possess a property referred to as spin, which is an intrinsic angular momentum, and can generally be thought of as the electrons spinning on its axis, which is pretty similar to how our earth spins on its axis. Then, the electron spin is quantized, meaning it can only have certain discrete values, either up or down.
Magnetic moment – the electron spin then gives rise to a magnetic moment that's usually visualized as a tiny bar magnet associated with the electron. The magnetic moment arises as a result of the circulating charge of the spinning electron, and its direction is aligned with the spin direction.
Magnetic fields and electron alignment – the thing is, in an atom, electrons usually occupy specific energy levels or orbitals around the nucleus, where each orbital is able to accommodate a certain number of electrons with opposite spin. Now, when these electrons within the atom occupy the same orbital, they have opposite spins, which leads to their magnetic moments cancelling each other out, resulting in no net magnetic effect.
Paramagnetism and ferromagnetism – for paramagnetic materials, they exhibit unpaired electrons in their atomic or molecular orbitals, which contributes to a net magnetic moment. In the presence of an external magnetic field, they are able to align with the field, thereby increasing the overall magnetization of the material. As for ferromagnetic materials, they exhibit spontaneous alignment of magnetic moments in domains even in the absence of an external magnetic field. So, in these materials, neighbouring atoms' magnetic moments align spontaneously, which creates large-scale magnetic domains, resulting in a strong overall magnetization.
Magnetic Materials
Magnetic materialscan simply be categorized into three; ferromagnetic, paramagnetic, and diamagnetic, where each type exhibits different behaviours when interacting with magnetic fields. So, let's start with ferromagnetic materials, which are strongly attracted to magnetic fields, thereby becoming permanently magnetized. Now in the absence of an external magnetic field, these materials have randomly oriented magnetic domains, but when exposed to a magnetic field, these domains align in the direction of the field, which results in a strong overall magnetization. And even after removing the magnetic field, this alignment tends to persist, making ferromagnetic materials ideal for creating permanent magnets. Secondly, we have paramagnetic materials which have unpaired electrons in their atomic or molecular orbitals. When exposed to a magnetic field, the materials become magnetized but then lose their magnetism when the external field is removed. And since these materials have a random orientation of the moments, the overall magnetization is relatively weak. Thirdly, diamagnetic materials are weakly repelled by magnetic fields and don't possess permanent magnetic moments like ferromagnetic and paramagnetic materials. So, when exposed to a magnetic field, these materials develop a temporary induced magnetic moment in the opposite direction of the applied field. This is a result of the orbital motion of electrons within the atoms or molecules.
Types of Magnets and the Common Shapes
There are different types of magnets based on their composition as well as how they are created. Here are some of the most common ones;
Permanent magnets – these are magnets that are commonly used and never lose their magnetic property once they are magnetized. They are basically made from materials such as iron, nickel, cobalt, or alloys such as neodymium-iron-boron (NdFeB) or samarium-cobalt (SmCo). They are widely used in various applications, which include generators, electric motors, magnetic clasps, and speakers.
Electromagnets – these are magnets that require an electric current to generate a magnetic field. The magnets consist of a coil of wire that is typically wound around a ferromagnetic core, through which the electric current flows, creating the magnetic field. This also means that when you turn off the current, the field is eliminated. These magnets are widely used, with the most common examples being electric switches, relays, magnetic lifting systems, as well as MRI machines.
Temporary magnets – these are, essentially, materials that become magnetized when exposed to a magnetic field but then lose their magnetism once the field is removed. These magnets are often used as temporary magnetization tools or in applications where magnetism is only required for a short duration. Some examples of these magnets include iron and steel.
Having looked at the types of magnets, let's look at the shapes. So, magnets come in various forms, which include the following;
Bar magnets – these magnets have a rectangular or cylindrical shape with equal-sized poles on each end, and they are commonly used for educational purposes as well as basic experiments.
Horseshoe magnets – they come in a U-shaped design resembling the shape of a horseshoe – hence the name. This means that the poles are closer together, which then provides a stronger magnetic field between the poles, and they are commonly used in applications requiring concentrated magnetic fields, such as generators and electric motors.
Disc/cylindrical magnets – the magnets have a round shape that resembles a coin or a cylinder and are often used in precast concrete, magnetic closures, jewellery clasps, or in small-scale applications where a compact magnet is needed.
Ring magnets – these are magnets that have a circular shape with a hole in the middle, and they are often used in applications that require a magnetic field passing through the center, which includes rotating machinery or sensors.
Block/cube magnets – these magnets come in a rectangular or cubic shape and are a mostly used in a number of applications such as precast concrete, speakers, magnetic separators, and magnetic levitation systems. They basically provide a large surface area for strong magnetic adhesion to the steel plates or embedded steel profiles in the formwork or moulds.
Real-world applications of magnets
Magnets have a wide range of practical applications across various industries and everyday life. Here are some notable real-world applications of magnets:
Precast concrete application - magnets are applicable in precast concrete manufacturing processes. Here is how they are applied;
· Formwork and moulds – precast magnets are used in formwork and moulds to hold the components in place during the casting process. You see, precast elements often require precise positioning and alignment, and the magnets are able to provide a strong and reliable method for securing the formwork for accurate and stable casting.
· Magnetic formwork systems – these are systems designed for precast concrete production and are able to utilize magnets embedded in formwork so as to create magnetic bond steel plates and magnetic beds
· Magnetic shuttering systems – just like the formwork systems, shuttering systems employ precast magnets to hold steel or composite shutters in place during the casting process, ensuring precise positioning and alignment.
Electric motors and generators – magnets convert electrical energy into mechanical energy and vice versa. The thing is, permanent or electromagnets are used to create magnetic fields that are able to interact with electric currents, generating rotational motion in motors and hence the production of electricity in generators.
Magnetic resonance imaging (MRI) – magnets are also used in MRI machines used in hospitals for medical imaging that is required for diagnosing and monitoring various health conditions.
Magnetic data storage - magnetic storage devices like hard disk drives (HDDs) and magnetic tape use magnets to store and retrieve digital information. The magnetic material on the storage medium is magnetized to represent data bits, which can be read and written using magnetic read/write heads.
Other uses include speakers and audio systems, magnetic separation and sorting, magnetic clasps, and fasteners, as well as on magnetic door catches.
Bottom line
In conclusion, we can agree that magnets are of crucial importance in our day-to-day lives, from healthcare, construction, manufacturing, transportation, and in modern technology. Beyond the realm of practicality, we also have to mention the fact magnets have captured our imaginations, fascinating both young and old alike. We mean, the invisible forces literary ignite curiosity and also inspire wonder and awe in the natural world. So, looking at how magnets work, we are able to get a glimpse of the invisible symphony of particles just dancing around in perfect harmony, which reveals yet another captivating layer of the grand tapestry of our universe.